As evidenced by the popularity of video sharing web sites, video is an increasingly important feature of the World Wide Web. In a typical scenario, a server hosts a file that stores all of the data of a video. When a user wants to use a client device to view the video, the client device requests the file from the server. In response to the request, the server sends data in the file to the client device, starting with data that represents the beginning of the video and ending with data that represents the end of the video. The client device may begin to present the video before the client device has received all of the data in the video file. This is known as “progressive download.” After the client device has completely downloaded all of the data in the video file, the client device may present any portion of the video without downloading any additional data from the server.